`x-list-fonts' on Windows 7

`x-list-fonts' on Windows XP worked fine with all Emacs versions starting
with 20 (at least).

On Windows 7 with Emacs 20, `x-list-fonts' systematically returns nil,
even when passed the value of the current frame's `font' parameter.

E.g., (x-list-fonts "-*-Courier-normal-r-*-*-14-112-120-120-c-*-iso8859-1")
returns nil, even though the current frame uses exactly that font.

I do not have Emacs 21 on Windows 7, but for Emacs 22 and later there is
no such problem.

Anyone have an idea about this?  I'm using a binary, not building Emacs 20,
and `x-list-fonts' is built in, so I imagine there is no solution, but
perhaps someone has an idea?